List system DM jobs

curl --request GET \
  --url https://api.fluxer.app/v1/admin/system-dm-jobs \
  --header 'Authorization: <api-key>'

{
  "jobs": [
    {
      "job_id": "<string>",
      "status": "pending",
      "content": "<string>",
      "target_count": 1073741823,
      "sent_count": 1073741823,
      "failed_count": 1073741823,
      "created_at": "<string>",
      "excluded_guild_ids": [
        "<string>"
      ],
      "approved_at": "<string>",
      "registration_start": "<string>",
      "registration_end": "<string>",
      "last_error": "<string>"
    }
  ],
  "next_cursor": "<string>"
}